was one of the most prominent Japanese photographers in the first half of the 20th century in Japan.
As an amateur photographer, he was very energetic in photography groups, such as Naniwa Photography Club (, Naniwa Shashin Kurabu) and Tampei Photography Club.
In 1937, he founded Avant-Garde Image Group (Avant-Garde Zoei Shà «dan, ) with Gingo Hanawa (1894âÂÂ1957, ), Yoshio Tarui, Kà Ârà  Honjà  and Yoshifumi Hattori. The Osaka section of the 2022 Tokyo Photographic Art Museum exhibition ' situated the group within the Kansai avant-garde and included Hirai among its artists.
In 1956, Hirai also participated in the newly founded Japan Subjective Photography League and in the First International Subjective Photography Exhibition, which brought together prewar avant-garde figures such as Kansuke Yamamoto and Kà Ârà  Honjà  alongside emerging postwar photographers including Kiyoji à Âtsuji, Ikkà  Narahara, and Yasuhiro Ishimoto.
He was good at imaginative, illusionary and surrealistic photography, using photomontages and color painting on prints. His works such as "Fantasies of the Moon" (, 1938), "Mode" (1938, , MÃ Âdo) and "Life" (1938, , Seimei) are known among other important works for the history of Japanese photography before World War II.